The use of tobacco products is associated with increased severity of periodontal destruction, manifest as increased gingival recession in smokeless tobacco (SLT) users and increased bone loss in smokers. The overall purpose of this study is to examine the role of nicotine in epithelial proliferation and collagen destruction and its effect on the inflammatory mediators implicated (PGE2 and IL-1) in these events. The hypothesis is that nicotine acts by stimulating production of these mediators, and that furthermore, the combination of nicotine and bacterial antigenic exposure may amplify the production of inflammatory mediators leading to enhanced tissue destruction. The project will be divided into three studies as follows. The first study will use a rat model to examine the effect of nicotine on oral epithelial proliferation (based on bromodeoxyuridine (BrdUrd) uptake) and collagen destruction. This will be related to PGE2 and IL-1 soft tissue levels as determined using enzyme- linked immunosorbent assay (ELISA) and bioassay, respectively. In the second study, the effects of tobacco products on gingival levels of inflammatory mediators in SLT users will be studied. In order to determine potential cell sources of inflammatory mediators and to examine any interactions between bacterial components and nicotine, the third study will measure production of inflammatory mediators in lipopolysaccharide (LPS) stimulated in vitro systems treated with and without nicotine. Mediator levels in this model will be quantified using ELISA. If mediators of inflammation are increased in the nicotine treated rat tissues and tobacco exposed human tissues in conjunction with histologic alterations, this would implicate such mediators in the etiology of periodontal tissue damage. The in vitro systems will provide important information regarding potential sources of inflammatory mediators and define the interaction of bacterial antigens and nicotine. This information would be valuable in explaining the mechanism of the observed clinical changes in both SLT users and smokers and may have therapeutic implications in the prevention and treatment of tobacco-induced tissue destruction.